Why doesn’t he feel ready? What is he afraid of?

I was abandoned a month ago. I was broken up with over the phone, through a long message, the day before our engagement anniversary. He said that he was feeling a lot of anxiety and that he no longer had feelings.

On the day of HIS birthday, last week, he wrote to me on his own initiative. It was a very sad message in which he remembered things about me. He said that he felt empty, but that he had to fill that emptiness by himself. However, he also made it clear that he did not want to enter a relationship again.

Since he left me, he has said that we should talk in person, but that he does not feel ready yet. Why doesn’t he feel ready?
What is he afraid of?

I should add that the relationship was very deep and very painful, marked by health-related events. I had the feeling that, in general, he still loved me but was extremely overwhelmed and frightened by the future. He had wanted to leave me for months.